Known angular velocity sensors (gyro) include: mechanical type sensors that use the precession of a rotating body; optical type sensors that use a change in timing to receive laser beams revolving in a rotating enclosure; and fluid type sensors that spray a sensing gas to a heated wire in an enclosure and detect variations of the amount of sprayed gas with the rotation of the enclosure via the temperature of the wire, for example.
Recently, there is a growing demand for angular velocity sensors in car navigation systems, vehicle's antiskid brake systems, and other systems to detect the orientation of a vehicle. Compared with the aforementioned types of sensors, inexpensive, light-weighted and compact vibration type angular velocity sensors are becoming a mainstream. The vibration type angular velocity sensors are configured to, when an angular velocity is exerted on an oscillator vibrating in a predetermined reference direction, detect a new vibration component (hereinafter referred to as “angular velocity vibration component”) based on a Coriolis force in a detecting direction orthogonal to the reference vibration direction, and output angular velocity information based on the detected vibration component. The following Patent Literature 1 describes a tuning-fork type angular velocity sensor as an exemplary configuration of the vibration type angular velocity sensor.
In the antiskid brake system of a vehicle, a value (command value) of a steering angle sensor installed in a steering wheel is compared with an output value (measured value) of an angular velocity sensor incorporated in the antiskid brake system to determine whether the vehicle is skidding. Based on the determination result, the engine output and braking forces of the four wheels are controlled so as to stop skidding of the vehicle body.
A rollover detection system of a vehicle determines whether the vehicle is rolled over or not based on an output value (measured value) of an angular velocity sensor built in the system, and inflates an airbag and further stops the feeding of fuel based on the result, thus preventing a secondary accident.
Each of these systems has to measure an angular velocity in a different detection direction. For instance, the antiskid brake system of a vehicle has to detect the rotation around an axis that is orthogonal to the ground. Meanwhile, the rollover detection system has to detect the rotation around an axis that is horizontal to the ground.
The detection range also may vary from one system to another. For instance, in the case of the antiskid brake system, relatively slow turn is a major control target, and the angular velocity sensor for this system has a relatively narrow detection range and high resolution. Whereas, since the rollover detection system aims to detect rollover caused by an accident, the angular velocity sensor for this system has a wider detection range and relatively low resolution. In this way, angular velocity sensors have to have a different detection direction, a detection range and resolution for each system.
The following Patent Literature 2 discloses the configuration including two angular velocity detection units having a revolving weight, in which an output signal from each angular velocity detection unit is calculated, thus detecting angular velocities and accelerations in two-axis directions. The following Patent Literature 3 discloses the configuration to perform calibration so that each of a plurality of angular velocity detection elements detects a change in angular velocity of a predetermined range.